1. Field of the Invention
The invention is in the field of biomass collection and preconditioning for subsequent refining into ethanol and other products. Specifically, the invention is directed to the collection of agricultural biomass over a large area so as to take advantage of economies of scale. According to embodiments, the biomass may be preconditioned to a selected pH, either in stockpiles, or at a centrally located plant prior to downstream processing.
2. Description of the Related Art
In the search for alternatives to petroleum as a transportation fuel, ethanol has been seen to be of promise, at least as a supplement to petroleum-derived gasoline. Ethanol is derivable from sugar using relatively simple technology, and it is very well-characterized in its properties and its health and environmental impact, humankind having produced ethanol (beer, wine and distilled spirits) for thousands of years. Further, ethanol has had an established use as a motor vehicle fuel for decades; the Ford Model T, first introduced in 1908, was capable of using either gasoline or ethanol as its fuel (or a mixture, as used by automobiles in the U.S. today).
At the present time, the ethanol used for fuel is largely made from corn, specifically the seed of the plant (kernels), although from a technological standpoint almost any grain or fruit can be used. The corn kernels consist largely of starch, which is readily converted to sugar. Most basically, the sugar derived from corn is fermented, typically using a yeast, which digests the material and produces ethanol as a product of yeast metabolism. Although simple and based on well-established technology, corn-derived ethanol has been criticized for being inefficient and diverting food to fuel use, thus making the price of corn, animal feed and livestock higher.
In contrast to grain ethanol, ethanol from agricultural, forest and similar biomass (also referred to herein as cellulosic ethanol) is seen to have great promise in energy efficiency and green house gas reduction. The particular biomass of interest is the structural portion of the plant, such as grass straw and corn stalks, or the woody portion of trees. This plant matter is made of lignin and cellulose, and is a not source of food for people. In ethanol manufacture, the lignin is separated and used for fuel and the cellulosic material is converted to sugars. The sugars are fermented as with the grain to ethanol.
Manufacturing cellulosic ethanol (i.e., ethanol derived from cellulose) is also advantageous because it is sustainable over the long term. In addition, use of biomass as a feedstock for ethanol manufacture can result in no net green house gas emissions, in fact if carbon dioxide from the fermentation step is collected and sequestered, the net green house gas emissions for the entire fuel cycle (field to wheels) is negative. This is because the agricultural biomass removes more carbon dioxide from the atmosphere while it is growing than is emitted during biomass transportation, biomass processing to produce ethanol (when carbon dioxide from fermentation is sequestered), ethanol transportation and ethanol combustion in the vehicle.
U.S. Pat. No. 4,461,648 to Patrick Foody, herein incorporated by reference in its entirety, discloses technology in which cellulose is made accessible for chemical reaction by a process of steam explosion and chemical disintegration to break down the bonds between the lignin and cellulose in the biomass. During the 1970's, after the first “oil shock” occurred, the inventor was conducting research on making low-grade fiber and wood digestible to ruminant animals. He recognized that accessibility of these materials to ruminant animal microflora and accessibility to enzymes was in fact a very similar problem. Trials were conducted using steam explosion to fractionate the fiber. As it turned out, it was a much more difficult problem than simply “exploding” the fiber to fractionate the internal bonds, and involved a very narrow window across the time/temperature range at which the process could be optimized. Nevertheless, the result of these efforts, disclosed and claimed in U.S. Pat. No. 4,461,648, was a process that made the cellulose completely accessible to enzymes. This was the first breakthrough in the technology and arguably laid the foundation for biomass refining, as the science is currently called.
U.S. Pat. No. 5,916,780, to Brian Foody, et al., herein incorporated by reference in its entirety, discloses technology for pre-treating and transporting biomass, especially as it relates to the production of ethanol.
In order to be viable, cellulosic ethanol must overcome advantages that accrue to its industrial competitors, the grain ethanol and petroleum industries. One of these advantages is that the road, rail, pipeline and river infrastructure for transporting conventional energy products is already in place.
Biomass of the type at issue hereby its nature is at a significant cost and handling disadvantage as compared to these competitors. For example, grain, which is free flowing, weighs 40 lbs to 50 lbs per cubic foot, while biomass weighs 10 lbs per cubic foot in bales, and 5 lbs per cubic foot loose. The largest grain ethanol plants being currently built, without access to water or rail transportation, handle on the order of 2,500 tons per day. At a “test weight” of 5 lbs per cubic foot, the viability of a biomass refining system is largely dictated by access to road systems. The differential in the volume to be moved could challenge the capacity of most road systems.
Because transportation constraints act as a limiting factor on the size of a biomass-processing plant, most biomass projects are built well below optimum size.
In order to take advantage of the cheaper unit cost of agricultural biomass, it is estimated that a system capable of processing significantly in excess of 2,500 tons per day of biomass would be necessary for cellulosic ethanol to compete with easily refined starch based grain ethanol.
The oil industry, the other conventional competitor to biomass refining, has the advantage of “scale” and well established pipeline systems so that it can tolerate significantly higher raw material costs.
It is estimated that a cellulosic ethanol system capable of processing in excess of 10,000 tons per day of biomass would be required to compete with oil.
Further technological and scientific advances in materials handling and physical layouts are necessary to make ethanol from biomass commercially competitive with oil, especially with regard to the economies of scale. Japanese Patent No. JP2002330644 proposes a system for biomass collection. However this patent discloses a pneumatic system and does not adequately address the implementation of a large scale biomass collection and refining system.
Pipeline systems for moving woodchips are not uncommon, but these are normally used on a point-to-point basis. Peter C. Flynn, et al., Bioresource Technology, 96 (2005) 819-829 postulates a biomass refining system wherein the water may be pumped back either completely or in part to the beginning of the system. This requires two pipelines, as noted by the author, and is not economically viable.
An important object of this invention is to overcome the difficulties and expenses that arise in connection with handling large amounts of relatively light non-free flowing biomass. The inventor herein has developed a “loop” system for moving a ligno-cellulosic feedstock slurry along the same pipeline as the transportation water, as well as adding new biomass at more than one selected point along the pipeline. According to embodiments of the present invention, conventional delivery systems, except for local pick-ups, can be avoided altogether, in favor of the centralized and integrated network of loops described herein.